An attempt will be made to compromise the efficiency of a regional lymphatic drainage system in cats infected with the lymphatic-dwelling filarial nematode, Brugia malayi. This will be accomplished by altering several aspects of the infection known to interfere with the function of the popliteal lymph node and the afferent vessels draining into this node. Studies showing that challenge with a Group G beta hemolytic streptococcus results in pronounced and persistent lymphedema in Brugia- infected cats will be extended to include an evaluation of the interaction between B. malayi and a dimorphic fungus, Sporotrix schenkii, which has a predilection for superficial lymphatic vessels. The correlation between foci of dead B. malayi in the lymphatics and the resultant tissue response following secondary microbial infection will be examined. Cats will be treated with an appropriate anthelminthic at levels known to kill different stages in the life cycle of B. malayi. This will be followed by challenge with an opportunistic streptococcus which produces pathology in limbs with lymphatic dysfunction but not in normal, previously uninfected limbs.